Alexander McQueen has always been complicated. McQueen loved to explore femininity and fashion in all its messy, contradictory glory; he was more interested in poking about in the dark corners of who we are and what we wear than in sketching make-believe dresses for happy-ever-after.

Sarah Burton, who succeeded him as creative director after his death, soon proved herself his equal in surprising and confusing the industry. When we thought we had her pegged as a shy talent uncomfortable in the spotlight, she confounded all by secretly designing the wedding dress of the decade. This coup was a sly, masterful piece of fashion-as-theatre that her former boss would undoubtedly have loved.

Still, until yesterday what seemed clear was that Burton's succession had ushered in a new era of serene femininity, a less fractious vision of beauty, at the house of McQueen. The Duchess of Cambridge's elegant wedding dress, and the precious, swan-like creatures who glided down last season's catwalk told us as much.

But the latest McQueen show blew those preconceptions out of the water. There was the model with her face entirely encrusted with shards of black jet and polished ivory shell, but her breasts bared under the finest veil. There was the pale pink cocktail suit in the finest Fortuny-pleated silk crepe, with the skirt demurely tailored to the knee but the jacket scooped to reveal a bra in a cobweb of coffee lace, all cinched by a glossy belt and finished with a lace gimp mask. There was even, in a black chiffon dress cut low at the back with open-laced corsetry, a suggestion of the infamous bumster collection.

And yet backstage, after this deliberately provocative display, Burton seemed taken aback by any suggestion that she had desired to shock. "I just wanted it to feel light," she said, in between being lifted into the air with delight by Emanuelle Alt, the editor of French Vogue, and effusively congratulated by Grace Coddington of American Vogue, who said the show sent shivers down her spine.

Let us not forget that backstage after her last catwalk show, in March, Burton swore blind to every journalist present that the wedding dress rumours that were to turn out to be entirely true were absolute rubbish. Her backstage edicts, then, can perhaps be taken with a pinch of salt. Indeed, Burton's official press release on the show allowed that "this is a collection about excess – an exploration of ideals of beauty at their most extreme".

Extreme beauty was not just a concept, here, but a reality. That is what made this show extraordinary: the bringing to life of a dreamlike, fantastical beauty. Even the first, simplest outfits were artworks, when seen at close quarters: a pencil skirt with close-pleats that undulate beguilingly over the hips but are dipped in gold at the hem to stiffen and exaggerate the silhouette, flattering the body like a gilt frame on a painting. Lace balaclavas with degradé edges so fine that the boundary between skin and lace is blurred, and corsets armoured with the overlapping petals of the finest shells.

And yet for every hint of chin-jutting aggression – the shiny, bondage-inspired corsets, the fetishistic lace-up boots – there was a complimentary dose of softness. The shoulders of an oyster-pink dress were scooped loose to reveal the skin beneath, where Lee McQueen would surely have added one of his signature exaggerated shoulders. Like I said, it's complicated.